This invention relates to a thermostat device which is responsible for cooling an internal combustion engine, and more particularly to a thermostat device which has lower flow resistance than a conventional thermostat, which can control the operation of a valve body regardless of the cooling water temperature at the time of engine start-up, and which can achieve early warming of the engine, an improvement in fuel economy, and the prevention of overheating by being able to control the flow rate of the cooling water which circulates through a heating circuit or the like.
Thermostat devices disposed in the cooling systems of internal combustion engines and the like comprise a sensor case having an in-built thermal expansion body which perceives temperature changes in cooling water which fills the circulation channels of a cooling system and expands and contracts accordingly. The valve body opens and closes in response to volumetric change accompanying the expansion and contraction of the thermal expansion body, and thus the thermostat device functions to maintain cooling liquid at a predetermined temperature.
An example of a conventional thermostat device is illustrated in FIG. 7. This thermostat device 1A comprises a thermostat operating section 30 which serves as the driving section of the valve bodies inside valve housing 31, 32, which is constituted by two members. The thermostat operating section 30 is fixedly supported by the valve housing 32, and a first valve body 33 and a second valve body 35 (bypass valve) are operated by an operating piston 9 which is built into the thermostat operating section 30, whereby a main channel 34 and a bypass channel 36 are controlled.
The housing 37 of the thermostat operating section 30 is supported by a holder 39, and this holder 39 surrounds the end of the housing 37 on the side at which the piston protrudes and the end of the opposite side in cap-form. The cap-form holder 39 is supported by the valve housing 32.
A central region with a pot-shaped cross section is provided in the first valve body 33, and the thermostat operating section 30 is disposed in this central portion. When the first valve body 33 is in a closed position, this central region, together with the holder 39, blocks the main channel 34.
A bolt 38 is provided as an extension in the axial direction of the operating piston (not shown) of the thermostat operating section 30. A second valve body 35 (bypass valve) is attached to this bolt 38 by a sliding guide and opens and closes a bypass channel 36. The second valve body 35 (bypass valve) is biased by a spring member 41. The first valve body 33 is biased by a spring member 40, and this spring member 40 is supported by the valve housing 31.
The thermostat device 1A constituted in this manner is disposed such that when cooling water from the enginei enters from the sleeve 42, this cooling water circulates from the bypass channel 36 to the engine or through the sleeve 43 to the radiatori. Directly after engine start-up, the cooling water is at a low temperature, and therefore the cooling water which enters from the bypass 36 is returned directly to the engine. When the cooling water reaches a predetermined temperature following the completion of engine warm-up, wax inside the housing 37 senses this temperature and expands accordingly, thereby causing the operating piston (not shown) of the thermostat operating section 30 to expand. As a result of the expansion of the operating piston, the first valve body 33 falls against the urging force of the spring member 40, thereby switching the main channel 34 from a blocked state to an open state, and the second valve body 35 (bypass valve) blocks the bypass channel 36. As a result, the cooling water from the sleeve 42 passes through the sleeve 43 and flows into the engine.
In order to force the wax inside the housing 37 to expand, a heating part 44 is provided in the housing 37, and this heating part 44 is caused to protrude from the valve housing 32 and connect to a superheater element 45.
In such a conventional thermostat device 1A, however, the housing 37 which serves as the cooling water temperature sensing portion is disposed inside the cooling liquid channels, and hence flow resistance in the cooling water entering from the sleeve 42 is large. It is therefore difficult to miniaturize the water pump which forces the cooling water to circulate.
Furthermore, during engine warm-up directly after engine start-up, the cooling water from the engine and the cooling water from the radiator become mixed in the vicinity of the housing 37, which may produce a hunting phenomenon. When such a phenomenon is produced, the temperature of the cooling water which flows into the engine becomes unstable, making it difficult to improve fuel economy and achieve early warming. As a preventative measure, it has been necessary to adjust the structure of the valve housing 32 or to attach a current plate, also known as a baffle plate, directly before the housing 37 which serves as, the temperature sensing portion in order to mix the cooling water.
Moreover, when the thermostat device 1A is disposed for inlet control, cooling water entering from the radiator is sometimes perceived, and as a result, malfunctions such as overheating may occur. Also, with the aim of compressing engine warm-up time, some devices are constituted such that the bypass valve body is closed and the flow rate of the cooling water flowing through the bypass channel is reduced to a minimum or halted completely, even when the temperature of the cooling water is low prior to engine warm-up, in order to avoid heat radiation from the bypass channel or from a heater radiator for heating the vehicle interior or various devices for controlling the engine provided at points in the bypass channel. However, since the flow of cooling water virtually ceases, heat spots may occur in the interior of the engine, or breakdowns of the engine or the thermostat may occur due to the negative suction pressure on the water pump.
If a further valve body is provided separately from the main valve body and bypass valve body in order to provide separate control for a heater radiator for heating the interior of the vehicle or various device circuits for controlling the engine, or if these circuits are integrated and controlled by the bypass valve body only, then the bypass channel has to be enlarged, whereupon problems arise such as construction becoming more complicated and the size of the device increasing.
The thermostat device according to the present invention has been devised in consideration of these problems, and it is an object of the present invention to provide a thermostat device in which early warming of an internal combustion engine can be achieved even at engine start-up time, in which fuel consumption can be reduced, and in which flow resistance of cooling water is low.
In order to solve the aforementioned problems, the thermostat device according to the present invention has a constitution in which a first valve body and a second valve body are removably supported on a main shaft which is supported by the distal end of a piston of a thermo-element which causes the first valve body and second valve body to open and close by sensing the temperature of cooling water, a temperature sensing section of the thermo-element is disposed so as to sense cooling water temperature by contacting only the cooling water from the engine outlet side without directly contacting the cooling water from the radiator outlet side, and a heat-generating element is attached to the temperature sensing section. Thus, in addition to the opening and closing of the first valve body and second valve body by the thermo-element in accordance with the temperature of the cooling water, the opening and closing of the first and second valve bodies are freely controlled by the application of a current to the heat-generating element.
According to such a constitution, a temperature hunting phenomenon in the cooling water temperature, which is produced when cooling water cooled to a low temperature in the radiator flows into the device all at once immediately after the opening of the first valve body, can be prevented, and an improvement in fuel economy and rapid heatingii of the cooling water can be achieved. Thus, since the cooling water is mixed directly before the housing which serves as the temperature sensing portion, there is no need for any structural improvements to the valve housing or to install a current plate.
The device also has a constitution comprising: upper housing in which a first influx sleeve through which cooling water enters from the engine outlet and a second influx sleeve through which cooling water enters from the radiator are disposed so that the cooling water in each of the sleeves does not mix, and in which the first valve body is disposed such that the thermo-element opens and closes the second sleeve through which cooling water enters from the radiator by sensing the temperature of the cooling water from the first influx sleeve; and lower housing in which a mixing chamber is formed for mixing the cooling water from the engine outlet, or the cooling water from the engine outlet and the cooling water from the radiator, and a main channel is formed for emitting the cooling water from the mixing chamber to the engine.iii 
By respectively forming the channel and the mixing chamber in the interior of the housing in this manner, the interior structure of the thermostat device can be simplified, the housing itself can be constructed integrally from a resinous material such as heat-resistant plastic, and thus the thermostat device can be made responsive to unitization.
The device also has a constitution in which a third influx sleeve is formed in the lower housing so that the cooling water from a heater for heating the interior of a vehicle and cooling water which circulates through various internal combustion engine control devices can be controlled to flow into the mixing chamber by means of the opening and closing of the second valve body.
According to such a constitution, the flow rate in the bypass channel can be reduced without reducing or halting the flow rate in the heater circuit or various device circuits, and as a result early warming of the engine becomes possible.
Furthermore, the heater circuit and various device circuits can be provided completely independently of the bypass channel, and therefore, for example, the influx inlet for cooling water from the engine outlet can be directly attached to the cooling water outlet of the engineiv.
It is also possible to improve the cooling efficiency of the engine when the temperature of the cooling water is high by using the second valve body to reduce or halt the flow rate in the heater circuit and various device circuits, thereby relatively increasing the radiator flow rate. Early warming of the engine, an improvement in fuel economy, and prevention of overheating may also be achieved.
Further, the device has a constitution in which the third influx sleeve is disposed below the second valve body, the first valve body is disposed above the second valve body, the thermo-element is disposed above the first valve body, and the first influx sleeve is provided between the thermo-element and the main valve.
According to such a constitution, there is no need to dispose the thermo-element inside the cooling water channel inside the housing, and thus flow resistance in the cooling water can be reduced and the structure of the thermostat device can be simplified and reduced in size. Furthermore, by varying the flow rate from the first influx sleeve, or in other words altering the diameter of the sleeve to alter the flow rate ratio with the other channels, the responsiveness of the thermo-element can be easily modified. The balance with the heating value of the heat-generating element can also be easily adjusted.
The device also has a constitution in which the thermo-element is disposed such that the cooling water from the first influx sleeve only comes into contact with one part of the temperature sensing portion of the thermo-element, and a heat-generating element is provided outside of the cooling water channels.
According to such a constitution, the amount of cooling water which is temperature-sensed by the thermo-element may be easily altered simply by modifying the interior structure of the housing, and thus the responsiveness of the thermo-element can be easily modified. The balance with the heating value of the heat-generating element can also be easily adjusted.
Moreover, by disposing the heat-generating element outside of the cooling water channels, electrical reliability and maintenance can be enhanced.